问题
单项选择题
DQDB同时支持 (26) 两种服务。DQDB子网的双总线结构由 (27) 总线以及接在这两条总线上的大量的节点组成。DQDB网络为双总线提供了 (28) 访问控制方式，其中能够提供非等时服务是 (29) ，它用于 (30) 业务。
A．预先仲裁访问
B．时分多址访问
C．排队仲裁访问
D．载波监听多路访问
答案
参考答案：C
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DQDB同时支持 (26) 两种服务。DQDB子网的双总线结构由 (27) 总线以及接在这两条总线上的大量的节点组成。DQDB网络为双总线提供了 (28) 访问控制方式，其中能够提供非等时服务是 (29) ，它用于 (30) 业务。
A．预先仲裁访问
B．时分多址访问
C．排队仲裁访问
D．载波监听多路访问
参考答案：C
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| You must know the "ding dong ditch". Person A rings Person B's doorbell, and then quickly runs away or hides before Person B answers. Person B hurries to answer the door, only to find that no one's there. After the 1 thing is repeated several times, this is called "ding dong ditch". Sharon Mardis, a single mother of four, told ABC News that she 2 a "ding dong ditch" when she 3 to her door at 1:00 am last night. "My doorbell started ringing, 4 I came to the door," Sharon told ABC News. "There was 5 at the door. I went back in the house. I got ten or twenty 6 and the doorbell started ringing again. I came back to the door, still nobody at the door." She got 7 and stepped outside, shouting, "Who's that? What on earth are you going to do?" There was just 8 . But after Sharon returned to the house, she 9 something. Smoke! Sharon quickly 10 her kids and the family pets and ran out of the house. Only then did she 11 how bad the fire was. The 12 of the house fell down; the house was quickly 13 by flames. The smoke detectors (探测器) had never 14 : they were out of batteries. Good thing for the doorbell. The 15 is who had rung it. 16 found that the flames has fused (熔化) the wires of the doorbell together, causing it to ring. But 17 , the fire had nothing to do with the doorbell wiring at all. It had started in the bathroom, well down the hall. From there, the flames didn't spread to the nearby 18 , where the children and Sharon were sleeping. 19 , they surprisingly reached the doorbell first, making it ring repeatedly, and 20 Sharon to avoid danger. Sharon believes it happened that way thanks to an angel. | ||||
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